Apparatus for radio communication.



G. W. PICKARD.

APPARATUS FOR RADIO COMMUNICATION.

APPLICATION FILED IAN-15,1913.

Transformer 6-H Condenser CbnaEnser E5 .Defe cfor.

In Vn tor:

/ 4 by K" Patented Mar. 28, 1916.

GREENLEAF WHITTIER PICKARD, OF AMESBURY, MASSACHUSETTS, ASSIGNOR TO WIRELESS SPECIALTY APPARATUS COMPANY, OF BOSTON, MASSACHUSETTS, A COR- v PORATION OF NEW YORK.

APPARATUS FOR RADIO coMMunIcArIon.

Specification of Letters Patent. Patented Mar. 28, 1916.

v 1 Application filed January 15,1913. Serial No. 742,101.

To all whom it may concern:

Be it known that I, GREENLEAF WHITTIER YPIGKARD, a citizen of the United States of America, and a resident of Amesbury, Massachusetts, have invented certain new and useful Improvements in Apparatus for Radio Communication, the principles of which are set forth in the following specification and accompanying drawing, which disclose the form of the invention which I now consider to be the best of the various forms in which the principles of the invention may be embodied.

This invention relates to improvements in apparatus for radio communication, and consists of'the combination and arrangement of the circuits and apparatus herein disclosed, with more particular reference to the testing set used with the receiving apparatus for the purpose 'of enabling an operator to determine and preserve the operative condition of his receiving apparatus.

The object of the invention -is.to obtain a testing outfit or set which will function accurately, the lack of such functioning having been a fault in prior sets.

The drawing is. a diagrammatic illustration of two embodiments of the invention, A and B. i

As is well known, the function of the test set is to, produce a-local disturbance which shall have an effect on the receiving apparatus which shall be comparable as nearly as possible to the eifect on the receiving apparatus of signals transmitted from a distant sender with which it is desired to maintain communication. If such function of the test set is efiiciently executed, the operator may be assured, substantially, that his receiving apparatus is in effective working condition, and specifically that it is in the best possible condition for working with a distant sender having known characteristics,

although this has not been possible heretofore.

. One of the principal faults in the previous test sets has been that they do not produce in the receiving circuit, oscillations of the 1 same character as those resulting from radio are used, an adjustment of the receiving apparatus and detector, which gives the maximum response, as in the head-telephones, to the local disturbances in the test set, is not the best adjustment for signals from a distant sending-station; all this being irrespective of the wave-length or tuning. In short, a good adjustment for the test set signals has been a poor adjustment for distant radiations, and a good adjustment for distant radiations has not given a maximum response to the test signals. The reasons for such defect of prior test sets have not been fully investigated or determined, but the apparatus and arrangement herein disclosed I have discovered to be highly advantageous in substantially eliminating the defects above referred to, and in providing certain important additional advantages.

In the drawing, I indicates an inductance (as the secondary of the oscillation transformer), belonging to any suitable receiving circuit, which-inductance may not only be adjustable as to the number of turns in circuit (as indicated by the single arrow on Either of the test sets A or B may be em ployed, and they are both shown in the single drawing here for convenience. The coil of the test set, N or N is preferably located a considerable distance, as-about a foot, from the receiving circuit inductance I, in its average or normal position, for the reason that it is usually best, in long distance signaling, to adjust the receiving apparatus and the detector to feebleimpulses corresponding with those received from far distant sending apparatus The coils N or i N may consist of only a singleturn of wire,

as shown.

The operation of test set A is. as follows: The closing of switch or key Y causes current from battery B to flow through the buzzer-Winding R, the movable buzzerarmature A and the stationary contact C, back to the batteryiby way of key Y; this energizes the buzzer magnet and causesxmovement of armature A and consequent breaking of the circuit at A, C. Forthwith, at

the instant of occurrence of the break, an.

' electromotive force occurs across 0, A which charges variable condenser V. Immediately after this the contacts A, '0 again close,

' whereupon charged condenser V discharges through the closed circuit N,A, C, and sets up oscillations in that circuit, the period or wave-length of which depend solely upon the capacity of condenser. V and the induc-' tance of loop N. This frequency, by adjustment of condenser V (or change in inductance of loop N, or both) may be made of any desired value, preferably that to which the receiving circuit is adjusted or at which it is generally used. The operator, repeatedly working the test set by key Y, also varies the adjustment of the detector itself until a response of maximum i tensityis observed in the usual telephone recelvers or their equivalents in the receiving apparatus.

Embodiment B is the same as A save for a change .in the connections of A, C and V, and for the use of an additional condenser K. As in A, oscillations are'set up in oscil lation circuit N, V by the electrical impulses resulting from the action' of the make-and-break at C A Here, however,

. A, C is directly in series with both the battery B and inductance N and the branch connection includes variable condenser V so that a charge in the oscillating circuit N -V is free to continue tooscillate, while the battery circuit is open at C A irrespective of other conditions at A C3 or any of the restof the apparatus. This differs from embodiment A, wherein the oscillating circuit N, V is closed only by way of A, O.

The other difference from embodiment A which may be.included in embodiment B, is the useful employment of the extra condenser K of relatively large capacity, connected as shown. This acts solely as a shunt to buzzer-coil R and its function is to make the circuit N 0 A K, Y ,'B of small I impedance to an abrupt current change, so

that when contacts C A separate from each other, a very sharp impulse is given to circuit N V I Embodiment B is preferable toA in that it-c onstitutes a more efiicient circuit, probably because a larger current flows throughthe oscillation circuit. But since efliciency' in such respect is not .so important as exact .radiated from ,a distant sender.

ceiving circuit is inductively coupled (I, N

or I, N and tuned (arrow in circuit at I),

to the buzzer circuit, or the latter circuit to The adjustment of the receiving circuits and detector which gives the maximum response to the operation ofjthe test set, is, for the first the former (variable condensers V or V time, in this invention, the same adjustment whichwill give the maximumresponse to waves transmitted" from a distant station.

The adjustment, (bodily movement) of the receiving-circuit-inductance I permits a variation over wide limits of the intensity of the test signals as effective on the telephones, while yet utilizing what is the normal ad justment of inductance I for other purposes,

including that of coupling-variation between v the primary and secondary of the oscillation transformer of the receiving apparatus. -In short, all the essential conditions of signaling over varying distances of great length may be by this invention operatively dupli-- cated in respect of thetest set. I claim 1. A testing apparatus for a receiver for-- radio-communication, which comprises an v electrical oscillations therein, said means-inoscillating circuit and means for producing eluding an electromagnetically operated make-and-break device, and a condenser oflarge capacity connected-in shunt to the coil of said device, to permit the giving of a sharp impulse to said" oscillating circuit by the make-and-break device.

2. In the art of radio communication, the combination with a tuning inductance of a receiving apparatus, constituting the sec ondary of the oscillation transformer, which inductance is adjustable as to the number of its turns in the receiving circuit whereby it may be tunedto the wave-frequency of a spark from a distant transmitter, of a test-- lng apparatus in proximity to said tuning inductance and comprising an oscillating circuit, and means for producing electrical oscillations therein, said oscillatory circuit including lumped inductance and capacity, and being adjustable as to its periodicity, whereby the latter may be made to correspond-with the wave-frequency of a distant transmitter and also to the period to which the receiver is tuned by the adjustability of said tuning inductance; said. lumped induc- 'nals from the testing apparatus, in addition to their frequency, maybe made to correspond with that of the signals from the distant transmitter.

GREENLEAF WHITTIER PIGKARD- In presence of- W. H. SEABURY, N. GENTLEMAN. 

